1. Field of the Invention
The present invention relates to a transmission line substrate having a coplanar line, and more especially to a transmission line substrate that can transmit signals over a broad band.
2. Background Art
A transmission line substrate having a coplanar line has been known (for example, refer to Japanese Patent Laid-Open No. 2000-244209). In some cases, the ground conductor of the coplanar line has two potentials. In this case, in a conventional transmission line substrate, two ground conductors having different potentials were AC-coupled.